The invention relates to constant velocity fixed joints. In particular, the invention relates to a constant velocity fixed joint in the form of a six-ball joint having the following characteristics: an outer joint part forming a bell-shaped member which comprises a first longitudinal axis, a base, an aperture and outer ball tracks; an inner joint part forming a hub which comprises a second longitudinal axis and inner ball tracks; the outer ball tracks have center lines which are curved and extend in planes through the first longitudinal axis, and comprise circumferentially alternately arranged three first outer ball tracks and three second outer ball tracks; the inner ball tracks have center lines which are curved and extend in planes through the second longitudinal axis, and comprise circumferentially alternately arranged three first inner ball tracks and three second inner ball tracks; the first outer ball tracks and the first inner ball tracks, together, form three first track pairs and the second outer ball tracks and the second inner ball tracks, together, form three second track pairs; the track pairs each accommodate a torque transmitting ball and tangents at the balls in the points of contact with the track pairs lying in planes through the longitudinal axes or in planes being parallel thereto form control angles with one another; the three first track pairs form control angles which open towards the aperture in the outer joint part; the three second track pairs form control angles which open towards the base of the outer joint part; a ball cage is positioned between the outer joint part and the inner joint part and comprises circumferentially distributed cage windows for one ball each, which cage windows hold the balls in one plane; the outer joint part comprises a substantially internally spherical guiding face for the ball cage, the ball cage comprises an externally spherical sliding face which is in sliding contact with the guiding face and ensures axial positioning.
Joints of this type are known as UFC joints (undercut-free counter grooves) or ACC joints (angular contact counter grooves), depending on whether the track center lines are formed by circular arches forming undercuts and being offset relative to one another (AC) or whether the track center lines in each of the joint parts, if viewed axially, are undercut-free and are composed especially of circular arches and adjoining straight lines (UF).
As said second track pairs are wedged towards the aperture of the outer joint part, the second outer ball tracks in the plane of the aperture form only relatively small widened regions in the guiding face of the outer joint part, as a result of which the introduction of the ball cage into the outer joint part is obstructed and can only be achieved, for example, by removing a substantial amount of material from the outer joint part. As a result, the amount by which the balls are enclosed by the ball tracks at the track end is reduced, which, in turn, reduces the torque transmitting capacity. In prior art joints, the ball cage is introduced into the outer joint part in a position whichxe2x80x94with reference to a position which is co-axial relative to the outer joint partxe2x80x94is rotated by 90xc2x0 around a transverse axis through its center. Herein, in the aperture plane of the outer joint part, a web region between two ball tracks engages a cage window opening.
It is an object of the present invention to provide a joint of said type which, while making optimum use of the material used for the enclosure of the balls by the ball tracks in the outer joint part at the track end, offers a greater degree of design freedom in respect of ball sizes and the axial extension of the guiding face while providing more advantageous assembly conditions. It is also an object of the invention to provide a method of introducing the cage into the outer part of such a joint.
According to the present invention, the foregoing objects are achieved by a constant velocity fixed joint wherein the guiding face in the outer joint part is widened by two recesses which start from the joint aperture and extend approximately in parallel and cylindrically into the joint interior, whichxe2x80x94with reference to one (I) of the second outer ball tracksxe2x80x94are positioned between the two (II) first outer ball tracks immediately adjoining said one (I) of the second outer ball tracks and the two (III) second outer ball tracks again immediately adjoining said two (II) first outer ball tracks. The cross-sectional contour of the recesses, while observing an assembly play, is defined by the radial elevational contour of the ball cage when the latter, by means of a central plane thereof, is positioned perpendicularly on a central plane through said one (I) of the second outer ball tracks and brought into simultaneous contact with the two (II) first outer ball tracks immediately adjoining said one (I) of the second outer ball tracks. In addition, the ball cage is offset from a symmetric central position in the aperture towards said one (I) of the second outer ball tracks by an offset OFF.
This design measure eliminates the restriction to which prior art joints were subjected in respect of the relation between window width in the ball cage and web width between two ball tracks in the outer joint part in view of a possible introduction of the cage into the outer joint part. At the same time, this design measure offers the possibility of providing guiding faces in the outer joint part with optionally a longer or shorter axial extension.
Concrete embodiments can be characterized by the following features: the cross-sectional contour of the recesses is defined by a circular arch of diameter D which is greater than or equal to the diameter d of the guiding face in the plane of the joint aperture and greater than a relative maximum cross-section assembly dimension m at the sliding face of the ball cage; the cross-sectional contour of the recesses is formed by wedges which are symmetric relative to one another and whose flanks positioned towards said two second outer ball tracks form an angle of approximately 60xc2x0 relative to one another; the cross-sectional contour of the recesses is defined by a circular arch with a radius which is slightly greater than the radius of the sliding face of the ball cage and which is offset from the central joint axis towards said one of the second outer ball tracks.
As can also be seen in the preferred embodiments described below, the outer joint part can comprise a base which is integrally formed on or, alternatively, attached by friction welding.
The inventive method of introducing the cage, as a function of the design, is characterized in that the ball cage, when one of its central radial cross-sections passes through the plane of the aperture of the outer joint part, is directed with its axis to said one of the second outer ball tracks and is offset from a symmetric central position in the aperture towards said one of the second outer ball tracks by an offset OFF wherein, especially, the ball cage, when one of its radial cross-sections passes through the plane of the aperture of the outer joint part, is rotated around its axis in such a way that, in the radial elevational contour, two cage windows are visible in the sliding face of the ball cage in a chamfered manner, i.e. the plane of the aperture centrally intersects two radially opposed cage windows.